The present invention is directed to a circuit for controlling a valve regulating a surfactant mixed with water. The present invention also relates to a compressed-air-foam-system of a soap type surfactant mixed with water to provide a foam solution.
The present invention is directed to a circuit for controlling a valve regulating a surfactant mixed with water, which comprises a signal generator electrically coupled with a first sensor for sensing the conductivity of the water and with a second sensor for sensing the conductivity of the surfactant. It also includes circuit means for converting the difference between the conductivity of the water and the conductivity of the surfactant into a voltage. It also includes control means for controlling the valve using the voltage produced by the circuit means and a control voltage.
The present invention is also directed to a circuit for controlling a valve regulating a surfactant mixed with water, which comprises a sine wave generator for generating a sine wave signal coupled with a first sensor for sensing the conductivity of the water and a second sensor for sensing the conductivity of the surfactant, wherein the sine wave signal is modulated by the first and second sensor forming a first modulated sine wave and a second modulated sine wave. It also includes an oscillator, wherein the oscillator controls a pair of switches used to switch the sine wave signal from the first sensor to the second sensor repeatedly, such that a single circuit path may be used for both sensors. It also includes direct current restore circuitry for converting the first and second modulated sine waves to a first and second direct current signal. It also includes a low pass filter for removing any high frequency components from the first and second direct current signals. It also includes timing circuitry for sampling and holding the first and second direct current signals and for placing the first and second direct current signals on separate circuit paths. It also includes a differential amplifier for comparing the first and second direct current signals to produce a differential voltage. And it also includes control loop circuitry for using the differential voltage and a control voltage to regulate the valve.
The present invention also relates to a compressed-air-foam-system of a soap type surfactant mixed with water to provide a foam solution, comprising a water source in fluent contact with a first sensor for sensing the conductivity of the water. It also includes a foam solution source in fluent contact with a valve and a second sensor for sensing the conductivity of the surfactant. It also includes circuit means for converting the difference between the conductivity of the water and the conductivity of the surfactant into a voltage. And it also includes control means for controlling the valve using the voltage produced by the circuit means and a control voltage.
Additional objects and advantages of the invention will be set forth in the description which follows, and in part will be obvious from the description, or may be learned by the practice of the invention. The objects and advantages of the invention may be realized and obtained by means of the instruments and combinations particularly pointed out in the appended claims. These and other objects and features of the present invention will become more fully apparent from the following description and appended claims, or may be learned by the practice of the invention as set forth hereinafter.